This invention relates to the production of a synthesis gas (syngas) using an autothermal reactor (ATR) and a reforming exchanger.
Reforming of hydrocarbons is a standard process applying a plurality of generally endothermic reactions for the production of hydrogen-containing synthesis gas used for manufacturing ammonia or methanol, for example. A conventional autothermal reforming reactor (ATR) is a form of steam reformer including a catalytic gas generator bed with a specially designed burner/mixer to which preheated hydrocarbon gas, air or oxygen, and steam are supplied. Partial combustion of the hydrocarbon in the burner supplies heat necessary for the reforming reactions that occur in the catalyst bed below the burner to form a mixture of mostly steam, hydrogen, carbon monoxide (CO), carbon dioxide (CO2), and the like. Effluent from the steam reformer is then usually further converted in shift converters wherein CO and steam react to form additional hydrogen and CO2, especially for ammonia or other syntheses where hydrogen is a main desired syngas constituent.
Advantages of ATR are low capital cost and easy operation compared to a conventional catalytic steam reformer, for example. Disadvantages of commercial ATR processes are the capital costs, operating difficulties, and plot area requirements associated with the air separation unit (ASU), especially where operating personnel and plot area are limited or other factors make an ASU undesirable. Where the synthesis gas is used for ammonia production, low temperature distillation has been used to remove excess nitrogen and other impurities to obtain a 99.9% purity level.
The present invention addresses a need for producing hydrogen from an ATR without using an ASU and/or low temperature distillation, by operating the ATR with excess air, supplying the ATR process effluent to a reforming exchanger to provide heat for additional syngas production, and partially purifying the product hydrogen stream without the need for low temperature processing for nitrogen rejection. Reforming exchangers used with autothermal reformers are known, for example, from U.S. Pat. Nos. 5,011,625 and 5,122,299 to LeBlanc and U.S. Pat. No. 5,362,454 to Cizmer et al., all of which are hereby incorporated herein by reference in their entirety. These reforming exchangers are available commercially under the trade designation KRES or Kellogg, Brown and Root (KBR) Reforming Exchanger System.